Very high energy ultrasonics

The field of high power ultrasonics covers the power region where irreversible changes can be produced in the medium. In Table 1 are listed the more important effects and uses of high energy ultrasonics. The field is very large; useful applications now touch almost every industry. In the final column of the table approximate figures are quoted for the order of the ultrasonic intensity required in the various applications. In gases and liquids the intensities obtainable are severely limited. In liquids this limit is fixed by cavitation which sets in at a rather low level. Cavitation can be avoided by pressurization, and then very high energies can be transmitted. But this is inconvenient and seldom used in practice. The field of very high energy ultrasonics is therefore practically confined to solids, as indicated in the table.